1. Technical Field
The present invention relates to a method for driving a discharge lamp having a pair of electrodes, a driving device, and a projector including a light source incorporated with such a discharge lamp.
2. Related Art
The state of a discharge emission-type lamp changes in accordance with an operating time, and in particular, electrodes wear off while the lamp is being lighted and the shapes thereof change as time passes. For example, if a plurality of protrusions are grown from the tip portions of the electrodes, and the body portions of the electrodes wear off irregularly, the start point of arc may be moved or the arc length may be changed. For this reason, the luminance of a light source device and a projector may be deteriorated and the lifespan of the discharge lamp may be shortened.
As a method of coping with the wear of the body portions of the electrodes, a technology is known in which a lighting current equal to or more than a rated current value is supplied while the discharge lamp is being lighted in a steady-state, thereby restoring the shapes of the tip portions of the electrodes (see Japanese Patent No. 3840054).
However, in a method of restoring the surface of each electrode, which is worn off, by temporarily increasing a current value, the tip portion of the electrode is temporarily completely melted, and the arc length temporarily rapidly increases. For this reason, illumination may be deteriorated, and flicker and color irregularity may occur.
In a light source including an auxiliary mirror in order to efficiently converge light to be emitted forward, the electrode on the auxiliary mirror side is excessively deteriorated, and the pair of electrodes are deteriorated unevenly.